Possible memory leak when resetting session inside a loop

Hi guys.

I think there is a memleak in the session object when you reset your session attributes while looping via repeat/asLongAs/forever/etc. statements. I use session reset to mimic close workload model of the SUT.

Please see below.

The environment:

• current Gatling version: 2.3.1
• OS version: macOS High Sierra 10.13.6
• Gatling run via current SBT plugin (gatling/gatling-sbt-plugin-demo)

The steps:

• clone the newest gatling/gatling-sbt-plugin-demo project
• enable verbose logback output to see all requests/session bags
• edit the ComputerWorld simulation to run in a loop with session reset:

class ComputerWorld extends Simulation {
  val httpProtocol = http
    .baseURL("http://computer-database.gatling.io")
    .acceptHeader("""text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8""")
    .acceptEncodingHeader("""gzip, deflate""")
    .acceptLanguageHeader("""en-gb,en;q=0.5""")
    .userAgentHeader("""Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:31.0) Gecko/20100101 Firefox/31.0""")

  val computerDbScn = scenario("Computer Scenario").repeat(10, "repeat_counter") {
    pause(5).exec(_.reset)

    .exec(http("getComputers")
    .get("/computers")
      .check(
        status is 200,
        regex("""\d+ computers found"""),
        css("#add", "href").saveAs("addComputer")))

    .exec(http("addNewComputer")
    .get("${addComputer}")
      .check(substring("Add a computer")))

    .exec(_.set("homeComputer", s"homeComputer_${ThreadLocalRandom.current.nextInt(Int.MaxValue)}"))
    .exec(http("postComputers") 
    .post("/computers")
      .formParam("name", "${homeComputer}") 
      .formParam("introduced", "2015-10-10") 
      .formParam("discontinued", "2017-10-10") 
      .formParam("company", "") 
      .check(substring("${homeComputer}")))
  }

  setUp(computerDbScn.inject(
    atOnceUsers(1)
  ).protocols(httpProtocol)) 
}

• run the ComputerWorld simulation, i.e.: sbt "gatling:testOnly computerdatabase.ComputerWorld"
• observe the contents of the session in the logback output

Actual result: The size of the blockStack inside session increases with new instances of ExitOnCompleteLoopBlock added in each loop iteration, i.e.:

List(ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter), ExitOnCompleteLoopBlock(repeat_counter))

Moreover, the simulation loops forever instead of stopping after requested number of repetitions, which bothers me even more.

Expected result: There should be only one instance of ExitOnCompleteLoopBlock in the session, like it is when the session is not reset inside a loop. The simulation should stop after looping the requested times.

I hope you’ll be able to reproduce and fix this 😃

Thanks for the great piece of software and best regards, Adam

[slandelle]

Note that Session#reset will no longer remove Gatling internal attributes, including caches. Also note that Gatling 3 will support closed workload model.

[slandelle]

closed by 8164abd